--- /dev/null
+/*
+ * Copyright (C) 2007 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.music;
+
+import android.database.AbstractCursor;
+import android.database.Cursor;
+import android.database.DataSetObserver;
+import android.util.Log;
+
+/**
+ * A variant of MergeCursor that sorts the cursors being merged. If decent
+ * performance is ever obtained, it can be put back under android.database.
+ */
+public class SortCursor extends AbstractCursor
+{
+ private static final String TAG = "SortCursor";
+ private Cursor mCursor; // updated in onMove
+ private Cursor[] mCursors;
+ private int [] mSortColumns;
+ private final int ROWCACHESIZE = 64;
+ private int mRowNumCache[] = new int[ROWCACHESIZE];
+ private int mCursorCache[] = new int[ROWCACHESIZE];
+ private int mCurRowNumCache[][];
+ private int mLastCacheHit = -1;
+
+ private DataSetObserver mObserver = new DataSetObserver() {
+
+ @Override
+ public void onChanged() {
+ // Reset our position so the optimizations in move-related code
+ // don't screw us over
+ mPos = -1;
+ }
+
+ @Override
+ public void onInvalidated() {
+ mPos = -1;
+ }
+ };
+
+ public SortCursor(Cursor[] cursors, String sortcolumn)
+ {
+ mCursors = cursors;
+
+ int length = mCursors.length;
+ mSortColumns = new int[length];
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] == null) continue;
+
+ // Register ourself as a data set observer
+ mCursors[i].registerDataSetObserver(mObserver);
+
+ mCursors[i].moveToFirst();
+
+ // We don't catch the exception
+ mSortColumns[i] = mCursors[i].getColumnIndexOrThrow(sortcolumn);
+ }
+ mCursor = null;
+ String smallest = "";
+ for (int j = 0 ; j < length; j++) {
+ if (mCursors[j] == null || mCursors[j].isAfterLast())
+ continue;
+ String current = mCursors[j].getString(mSortColumns[j]);
+ if (mCursor == null || current.compareToIgnoreCase(smallest) < 0) {
+ smallest = current;
+ mCursor = mCursors[j];
+ }
+ }
+
+ for (int i = mRowNumCache.length - 1; i >= 0; i--) {
+ mRowNumCache[i] = -2;
+ }
+ mCurRowNumCache = new int[ROWCACHESIZE][length];
+ }
+
+ @Override
+ public int getCount()
+ {
+ int count = 0;
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] != null) {
+ count += mCursors[i].getCount();
+ }
+ }
+ return count;
+ }
+
+ @Override
+ public boolean onMove(int oldPosition, int newPosition)
+ {
+ if (oldPosition == newPosition)
+ return true;
+
+ /* Find the right cursor
+ * Because the client of this cursor (the listadapter/view) tends
+ * to jump around in the cursor somewhat, a simple cache strategy
+ * is used to avoid having to search all cursors from the start.
+ * TODO: investigate strategies for optimizing random access and
+ * reverse-order access.
+ */
+
+ int cache_entry = newPosition % ROWCACHESIZE;
+
+ if (mRowNumCache[cache_entry] == newPosition) {
+ int which = mCursorCache[cache_entry];
+ mCursor = mCursors[which];
+ if (mCursor == null) {
+ Log.w(TAG, "onMove: cache results in a null cursor.");
+ return false;
+ }
+ mCursor.moveToPosition(mCurRowNumCache[cache_entry][which]);
+ mLastCacheHit = cache_entry;
+ return true;
+ }
+
+ mCursor = null;
+ int length = mCursors.length;
+
+ if (mLastCacheHit >= 0) {
+ for (int i = 0; i < length; i++) {
+ if (mCursors[i] == null) continue;
+ mCursors[i].moveToPosition(mCurRowNumCache[mLastCacheHit][i]);
+ }
+ }
+
+ if (newPosition < oldPosition || oldPosition == -1) {
+ for (int i = 0 ; i < length; i++) {
+ if (mCursors[i] == null) continue;
+ mCursors[i].moveToFirst();
+ }
+ oldPosition = 0;
+ }
+ if (oldPosition < 0) {
+ oldPosition = 0;
+ }
+
+ // search forward to the new position
+ int smallestIdx = -1;
+ for(int i = oldPosition; i <= newPosition; i++) {
+ String smallest = "";
+ smallestIdx = -1;
+ for (int j = 0 ; j < length; j++) {
+ if (mCursors[j] == null || mCursors[j].isAfterLast()) {
+ continue;
+ }
+ String current = mCursors[j].getString(mSortColumns[j]);
+ if (smallestIdx < 0 || current.compareToIgnoreCase(smallest) < 0) {
+ smallest = current;
+ smallestIdx = j;
+ }
+ }
+ if (i == newPosition) break;
+ if (mCursors[smallestIdx] != null) {
+ mCursors[smallestIdx].moveToNext();
+ }
+ }
+ mCursor = mCursors[smallestIdx];
+ mRowNumCache[cache_entry] = newPosition;
+ mCursorCache[cache_entry] = smallestIdx;
+ for (int i = 0; i < length; i++) {
+ if (mCursors[i] != null) {
+ mCurRowNumCache[cache_entry][i] = mCursors[i].getPosition();
+ }
+ }
+ mLastCacheHit = -1;
+ return true;
+ }
+
+ @Override
+ public String getString(int column)
+ {
+ return mCursor.getString(column);
+ }
+
+ @Override
+ public short getShort(int column)
+ {
+ return mCursor.getShort(column);
+ }
+
+ @Override
+ public int getInt(int column)
+ {
+ return mCursor.getInt(column);
+ }
+
+ @Override
+ public long getLong(int column)
+ {
+ return mCursor.getLong(column);
+ }
+
+ @Override
+ public float getFloat(int column)
+ {
+ return mCursor.getFloat(column);
+ }
+
+ @Override
+ public double getDouble(int column)
+ {
+ return mCursor.getDouble(column);
+ }
+
+ @Override
+ public boolean isNull(int column)
+ {
+ return mCursor.isNull(column);
+ }
+
+ @Override
+ public byte[] getBlob(int column)
+ {
+ return mCursor.getBlob(column);
+ }
+
+ @Override
+ public String[] getColumnNames()
+ {
+ if (mCursor != null) {
+ return mCursor.getColumnNames();
+ } else {
+ // All of the cursors may be empty, but they can still return
+ // this information.
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] != null) {
+ return mCursors[i].getColumnNames();
+ }
+ }
+ throw new IllegalStateException("No cursor that can return names");
+ }
+ }
+
+ @Override
+ public void deactivate()
+ {
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] == null) continue;
+ mCursors[i].deactivate();
+ }
+ }
+
+ @Override
+ public void close() {
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] == null) continue;
+ mCursors[i].close();
+ }
+ }
+
+ @Override
+ public void registerDataSetObserver(DataSetObserver observer) {
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] != null) {
+ mCursors[i].registerDataSetObserver(observer);
+ }
+ }
+ }
+
+ @Override
+ public void unregisterDataSetObserver(DataSetObserver observer) {
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] != null) {
+ mCursors[i].unregisterDataSetObserver(observer);
+ }
+ }
+ }
+
+ @Override
+ public boolean requery()
+ {
+ int length = mCursors.length;
+ for (int i = 0 ; i < length ; i++) {
+ if (mCursors[i] == null) continue;
+
+ if (mCursors[i].requery() == false) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+}
OSDN Git Service
